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Title: Outstanding problems in nonequilibrium statistical physics : doctoral dissertation Authors: ID Faggian, Marco (Author) ID Ginelli, Francesco (Mentor) More about this mentor... ID Levnajić, Zoran (Comentor) Files: DR_2019_Marco_Faggian.pdf (14,36 MB) MD5: F79F59C4B1F7DC0AFC623866F772760D   Language: Slovenian Work type: Doctoral dissertation Typology: 2.08 - Doctoral Dissertation Organization: FIŠ - Faculty of Information Studies in Novo mesto Abstract: This PhD thesis is mainly devoted to the study of different problems in nonequilibrium systems that undergo certain phase transitions. The first part of this thesis constitutes a brief review of fundamental concepts in statistical physics. Many of them, of course, will be useful in the remaining of the thesis. My research is thus articulated in three main chapters. The second chapter focuses on a numerical and experimental evidence of an absorbing phase transition, so far associated with spatiotemporal dynamics provided in a purely temporal optical system. We provide a numerical and experimental study of an effective model for a bistable semiconductor laser, with long-delayed opto-electronic feedback and multiplicative noise showing the peculiar features of a critical phenomenon belonging to the directed percolation universality class. In the third part of the thesis we present a random network of heterogeneous phase oscillators in which the links mediating the interactions are constantly rearranged with a characteristic timescale and an extremely low instantaneous connectivity. We will show that, provided strong coupling and fast enough rewiring are considered, the network is able to reach partial synchronisation even in the vanishing connectivity limit. The last part is dedicated to a systematic test of an effective thermodynamics approach proposed for the identification of critical phase transitions in nonequilibrium systems by making a formal analogy with equilibrium systems. When the authors apply it to experimental data of neurons, this method seems to bring a signature of a "special critical point". However, the approach has never been tested on synthetic data and for this reason we will test it on out of equilibrium toy models that display critical transition in a known range of parameters. In the concluding section I summarise and briefly comment my main results and sketch some directions for further research. Keywords: statistična fizika, ravnotežna statistična fizika, neenakomerna statistična fizika, termodinamika, kritični pojavi, kritična točka, Kuramoto model, skupina za renormalizacijo, samoorganizirana kritičnost omrežja, Zipfov zakon, efektivni termodinamični pristop, doktorska disertacija Place of publishing: Novo mesto Place of performance: Novo mesto Publisher: [M. Faggian] Year of publishing: 2019 Year of performance: 2019 Number of pages: XII, 156 str. PID: 20.500.12556/ReVIS-5738  COBISS.SI-ID: 2048583955  UDC: 536.9(043.2) Publication date in ReVIS: 28.05.2019 Views: 3514 Downloads: 180 Metadata:    Cite this work Plain text BibTeX EndNote XML EndNote/Refer RIS ABNT ACM Ref AMA APA Chicago 17th Author-Date Harvard IEEE ISO 690 MLA Vancouver : FAGGIAN, Marco, 2019, Outstanding problems in nonequilibrium statistical physics : doctoral dissertation [online]. Doctoral dissertation. Novo mesto : M. Faggian. [Accessed 8 April 2025]. Retrieved from: https://revis.openscience.si/IzpisGradiva.php?lang=eng&id=5738 Copy citation

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License:	CC BY-NC-ND 4.0, Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
Link:	http://creativecommons.org/licenses/by-nc-nd/4.0/
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Licensing start date:	28.05.2019

Secondary language

Language:	English
Abstract:	Prvi del te disertacije predstavlja kratek pregled temeljnih konceptov statistične fizike. Mnogi od njih bodo seveda koristni v preostalem delu disertacije. Raziskava je tako predstavljena v treh glavnih poglavjih. Drugo poglavje se osredotoča na numerične in eksperimentalne dokaze o absorpcijskem faznem prehodu, ki so ga doslej povezovali s prostorsko-časovno dinamiko v izključno časovnem optičnem sistemu. V tem poglavju predstavimo numerično in eksperimentalno študijo efektivnega modela za bistabilni polprevodniški laser, z dolgo zakasnjenimi optoelektronskimi povratnimi informacijami in multiplikativnim hrupom, ki kaže posebne značilnosti kritičnega pojava, ki spada v razred usmerjene perkolacijske univerzalnosti. V tretjem delu disertacije predstavimo naključno omrežje heterogenih faznih oscilatorjev, v katerem so povezave, ki posredujejo med interakcijami, nenehno preurejene v značilnem časovnem razponu in izredno nizko takojšnjo povezljivostjo. Pokazali bomo, da je omrežje, v primeru močnega sklapljanja in dovolj hitrega ponovnega ožičenja, sposobno doseči delno sinhronizacijo tudi v mejah izginjajoče povezljivosti. Zadnji del je posvečen sistematičnemu preizkusu efektivnega termodinamičnega pristopa, predlaganega za identifikacijo kritičnih faznih prehodov v neravnovesnih sistemih, s formalno analogijo z ravnovesnimi sistemi. Ko jo avtorji uporabijo za eksperimentalne podatke o nevronih, se zdi, da ima ta metoda lastnost "posebne kritične točke". Kakorkoli, ta pristop še ni bil preizkušen na sintetičnih podatkih in zato ga bomo testirali na izven ravnovesnih modelih igrač, ki prikazujejo kritičen prehod v znanih razponih parametrov. V zaključnem delu so povzeti in na kratko komentirani glavni rezultati in orisane nekatere smernice za nadaljnje raziskave.
Keywords:	statistical physics, equilibrium statistical physics, nonequilibrium statistical physics, thermodynamics, critical phenomena, critical point, Ising, Kuramoto Model, renormalisation group, self organised criticality, time-varying networks, Zipf's Law, efective thermodynamics approach, doctoral dissertation

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